Pyrometer.



PATENTED JAN. 29, 1907.

G. HEELEY & 0. BEN.

PYRO METER.

APPLICATION FILED NOV.11,1905.

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GEORGE HEELEY AND CHARLES FERY, OF PARIS, FRANCE; SAID HEELEY ASSIGNOR TO LA COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D USINES A GAZ, OF PARIS, FRANCE.

Specification of Letters Patent.

Patented Jan. 29, 1907. t

To all whom, it may concern:

Be it known that we, GEORGE HEELEY and CHARLns FERY, citizens of the French Republic, and residents of Paris, in France, have invented certain new and useful Improvements in Pyrometers, of which the following is a specification.

This invention relates to a pyrometric telescope with a diaphragm intended for use in the measurement ofo the very highest known temperatures.

In the accompanying drawings, Figure 1 is a longitudinal section of a pyrometric telescope provided with the diaphragm device according to this invention, Fig. 2 being a front elevation of the diaphragm itself.

The telescope is constituted by a cylindrical body in which is adjustab'ly mounted a mirror a, secured to a toothed rack operated by a pinion d. At 6 is the soldered joint of a thermo-electric pile constituted by two wires, one of copper and the other of constantan, which is a well-known alloy of copper and nickel in equal parts. The wires are soldered crosswise in the center and connected at the ends to two rods or plates electrically communicating with two terminals c and f, which are electrically insu- At the end of a fixed cylinder p, near the soldered joint I), is arranged another small mirror. Heat and luminous rays entering the apparatus are reflected by the mirror at onto the mirror arranged at t, which sends the rays back into the eyepiece a, through which the hotbody is viewed.

The eyepiece c serves for focusing the hot body or mass the temperature of which is to be measured. This is done by varfying the position of the mirror a by means 0 the pinion d. When the apparatus is properly arranged, the heat-rays are concentrated at the conjugate focus of the point looked at, the said focus being at that moment at b. lf, for instance, the temperature of the sun is to bemeasured, the sun is looked at through the eyepiece c. A calorific and luminous image of the sun is obtained'at the conjugate focus of the sun relativel mirror. The conjugate focus an consequently the image move with the mirror of the telescope when the pinion d is rotated.

to thethe small mirror surrounding-the joint and reflecting into the e epiece c the rays already reflected by t e mirror a. the image of the sun is clearly visible in the eyepiece c, it is obvious that this image is formed in the mirror surrounding the oint b, and consequently-on the joint itself. It is a Well-known optical method for adjusting a telescope. The thermo-electric element being heated by the solar rays, its temperature rises. According to a well-known ph sical law a difierence of potential A is pro uced in the element and is in proportion to the difference of temperatures t t of the hot and cold part of the element.

When

This difference of temperature is obviously in proportion to the quantity of heat 1 received by the element.

t-t=K-g. This (juantity g is in proportion to the quantity o heat (1 of the image.

I g KI! 2/. This uantit g is in proportion to the quantity 0 heat emitted by the sun.

The quantity of Q as givenby the law of Stefan, Viennese physicist, (Wiener Alcademie, Berlin, Anno. 1879, t. LXXIX, pages 391-428,) is as follows: The uantity of heat radiated by a furnace or a lack body on another black body is in proportion to the difference of the fourth powers of the absolute temperatures of the two bodies. If T is the absolute temperature of the furnace and t the absolute temperature of the sol dered joint and Qthe quantity of heat radiated by the furnace, the above law will be' analytically expressed by the formula Q=A (T i The soldered joint can be considered as a black body. It is, in fact, covered with avarnish containing lampblack.

From the above equations the following Will-be obtained:

but the number t being negligible ared with T, we may write A J T The difference of potential A is indicated by any needle galvanometer. The galva nometer is graduated by taking as wellknowntemperatures the melting temperatures of silver, 962 oentigrade, and of gold, 1060 centigrade. The scale of the galvanometer is divided into centigrade degrees by applying the law of fourth powers.

The interposition of a mirror as the apparatus for concentrating the heat of the furnace on the soldered joint is indispensable in order to increase the quantity of heat to be measured.

in this apparatus the measurements are independent of the distance of the telescope from the furnace. In fact, when this distance varies it is necessary to vary the distance of the mirror a from the joint I; in order tofocus the hot body to bemeasured; but on this movement the angle a of the heat-cone which enters the fixed cylinder 19 in the joint I) is obviously constant. The angle a is independent of the distance of the telescope from the furnace. (w

In order to measure the temperature in the interior of a furnace, the apparatus is placed at four or five meters distance from the furnace and pointed at an opening in the walls of the furnace. The telescope is provided with a radial diaphragm, as shown in Fig. 2. The diaphragm 1s constituted by two fixed sectors 9 and h and two adjustable sectors 4, and j, which rotate together about a central pin 0. These adjustable sectors i and j carr an indicator 7c, moving on the circular .gra uation l, which enables the angles of active sectors n andm to be measured, the said angles varying from 0 to ninety degrees. The above diaphragm device has been adoptas comed in order to enable the highest temperature known to be measured with the same apparatus. When the apparatus is pointed at a furnace with a very high temperature,. the quantity of heat falling on the soldered 'oint is reduced by means of the diaphragm y reducing the free opening of the diaphragm, for it is necessary not to heat the joint of the thermo-electric element to a temperature above the melting temperature of the tin used for soldering the copper Wire to the other Wire. When pointed at the sun, for instance, the element would be melted.

The telescope being pointed with full openirig-that is to say, With the open parts m and a forming an. angle of ninety degrees-to a furnace Where there is silver at its meltingpoint of 962, the same deviation at thegalvanometer will be obtained bypointing the apparatus to a furnace containing platinum for such an angle a; as to give 2.32 and 17.9 being, respectively, the fourth powers of absolute melting temperatures of these two metals expressed in thousands of degrees and 15 being the fourth power of the temperature of the soldered jointthat is to say, 0.0086, which is negligible. In this Way we shall have, therefore,

90 2.32 ecs.s

that is, the angle which the needle k must show on the graduations l in order to have the same deviation at the galvanometer in both cases. It must be pointed out finally that this method of reducing the sensitiveness is the only one that it is possible to use, for the introduction of a resistance into the circuit of the galvanometer would reduce, it is true, the sensitiveness, but would not pre vent the increasing heating of the soldered joint, which could go as far as the meltingpoint. In fact, if an elevation of temperature of 40 is admitted for the joint pointed to molten silver it will be seen that by pointing the same joint to molten platinum we will obtain e 1-9- in 2.32 2.32

which is an excessive temperature capable of injuring the element and for which the proportionality of indications will no longer subsist.

What we claim as our invention, and desire to secure by Letters Patent, is-

1. The combination with a casing, of an eyepiece arranged at one end of the casing, a mirror within the casing, a second mirror Within the casing adapted to receive reflected rays from the first mirror and reflect said rays into the eyepiece, a thermo-electric pile the soldered joint of which is within the easing close to the said second mirror, and an adjustable diaphragm arranged atthe other end of the casin 2. The combmation With a casing, of an eyepiece arran ed at one end of the casing, a mirror adjustafiily'arranged within the easing, a second mirror within the casing adapted to receive reflected rays from the first mirror and reflect'said rays into the eyepiece, a therino-electric pile the soldered joint of which is within the basing close to the said second mirror, and an adjustable diaphragm arranged at the other end of the casing.

3. The combination with a casing, of an' 'within the casing adapted to receive reflected rays from the first mirror and reflect said V 'tTively to each other as described, and an inrays into the eyepiece, a thermo-electric pile the soldered joint of which is Within the casing close to the said second mirror, and an adjustable diaphragm arranged at the other .end of the casing, said diaphragm comprising fixed and rotatable sectors arranged relareflect said rays into the eyepieceja thermoelectric pile the soldered joint of which is Within the casing close to the said second mirror, and an adjustable diaphragm arranged at the other end of the casing.

5. A pyrometric telescope comprisin a casing, an eyepiece c, a thermo-electric pi e b,

' a mirror-cylinder p, an adjustable mirror a,

and an adjustable diaphragm g h i, substantially as set forth.

In testimony whereof We have signed our names to this specification in the presence of 2 two subscribing Witnesses.

GEORGE HEELEY. CHARLES FERY.

' Witnesses:

GEORGES BONNEUIL, T. W. OAULDWELL. 

